The present invention relates to a perpendicular magnetic recording medium and a method for manufacturing the same. In particular, the invention relates to a magnetic recording medium capable of high reliability and high density magnetic recording and a method for manufacturing the same.
Used as storage devices of mainframes, workstations, personal computers, and the like, magnetic disk drives have been becoming more important year by year with advancement in storage capacity and compactness. To allow a magnetic disk drive to have a larger storage capacity in a compacter body, it is necessary to raise the recoding density. Accordingly, commercialization of perpendicular magnetic recording drives is earnestly awaited since the perpendicular magnetic recording system allows higher recording densities than the conventional longitudinal magnetic recording system. As a magnetic recording medium, some perpendicular magnetic recording systems use a laminate of an adhesion layer, a soft magnetic layer, an intermediate layer and a granular magnetic layer formed on a rigid nonmagnetic glass or aluminum substrate plated with nickel-phosphorus.
Conventionally, a magnetic recording medium manufactured by using sputtering film deposition process is provided with a diamond-like carbon (DLC) protective film to protect the magnetic films from the sliding magnetic head. Such a DLC protective film is thinned down to 5 nm or thinner. Recently, it is also common to use a perfluoropolyether liquid lubricant on the protective layer to reduce friction between the magnetic head and the magnetic recording medium.
In Patent Document 1 (Japanese Patent Laid-Open No. Hei 4-90125), a DLC protective film is disclosed. Hydrocarbon radicals and hydrocarbon ions are deposited on a substrate by the chemical vapor deposition (CVD) method with hydrocarbon gas.
In addition, Patent Document 2 (Japanese Patent Laid-Open No. 2004-152462) discloses that reducing the hydrogen content of the DLC protective film to 35% or less is preferable when the flying performance of the magnetic head is taken into consideration.
In Patent Document 3 (Japanese Patent Laid-Open No. 2004-30803), a CVD method is disclosed which uses hydrocarbon-based gas and hydrogen to form a protective layer to protect a granular magnetic film on a nonmagnetic high polymer substrate. In addition, Patent Document 3 discloses that since a plastic substrate is used, applying no bias to the substrate is preferable.